Programmed manipulator apparatus

ABSTRACT

A programmed manipulator apparatus employs a continuously rotating memory drum in which may be stored signals representing a number of steps in a desired sequence of operations. A portable teach control assembly is employed during the teaching operation to establish a desired position of the manipulator arm which is then recorded on the memory drum. During repetitive work cycles, the recorded signals are used as command signals and are compared with encoder signals representing absolute position to move the manipulator arm to each set of positions in sequence. The manipulator arm may be moved over curved paths by employing artificial coincidence signals which are developed while large error signals still exist in the controlled axes. A common comparator and digital-to-analog converter is employed for all of the controlled axes which provides coincidence signals representing different magnitudes of error.

May 9, 1972 Renner et a1. gnals quence ofoperay is employed during esired position of the memory drum.

ignals are used as command signals and are compared with encoder signals ipulator arm to ipulator arm may ploying artificial coinrge error signals comparator and ignals representing 3 636 12/1966 3 407 12/1968 Renner et a1. 2 325 5/1960. Garber........... flelberger, 3 013 8/1966 Bullard 3 407 12/1968 Primary Evamz'ner-Everette A. Powell, Jr. Attorney-Mason, Kolehmainen, Rathburn & Wyss [57] ABSTRACT A programmed manipulator apparatus employs a continuously rotating memory drum in which may be stored si representing a number of steps in a desired se Mar. 18, 1969, tions. A portable teach control assembl the teaching operation to establish a d manipulator arm which is then recorded on the F1 During repetitive work cycles, the recorded 5 fi representing absolute position to move the man each set of positions in sequence. The man be moved over curved paths by em cidence signals which are developed'while la still exist in the controlled axes. A common digital-to-analog converter is employed for all of the controlled axes which provides coincidence 5 different magnitudes of error.

29 Claims, 24 Drawing Figures Horace L. Gardner,

am e. mmm .m u u LGBD United States Patent Dunne et a1.

[54] PROGRAMMED MANIPULATOR APPARATUS I [72] Inventors: Maurice J. Dunne; Joseph F. En

both of Newtown; Ridgefield; Torsten H. Lindbom, Newtown, all of Conn.

[73] Assignee: Unimat1on,lnc.,BetheLConn.

[22] Filed: Aug. 18, 1970 [21] Appl.No.: 64,802

Related US. Application Data [63] Continuation of Ser. No. 808,152

abandoned.

[51] Int.Cl.............. [58] FieldofSearch...............................

[56] References Cited UNlTED STATES PATENTS 2,927,258 3/1960 2,937,325 5/1960 3,269,013 8/1966 3,291,971 12/1966 PATENTEDMM 9 I972 sum 02 (1F. 13

sum 03 or 13 PATENIEBMM 9 I972 PATENTEDIIIII 91972 3,661,051

.SHEET 05UF13 TEACH CONTROLS-306 v T v 37' 510 20UT New 378 72 3|O OUT-IN 3 sERvO AMPL OUT'IN OUTW mg: 380;"? 0; a VALVE CYLIND R ENcODER T rlOO r324 SWIVEL I SWIVEL SW'VEL SERVO CYLINDER ESQ OD E R 382 & VALVE 64 [3M DOWN UP DOWN-UP DOWN-7UP a VALVE cYI INDER ENcODER 7 /9O r322 BEND BEND BEND BEND sse SERVO AMPL- CYLINDER ENCODER I a VALVE 7 /'|24.l?.6 32 ROTARY sER tl% lfll f-"L ROTARY ROTARY 388 Y a VALVE CYLINDER ENcODER 385 a ACC.SEL. of I 'I :81- 39W saI CLAMP oON 0FF CONTROL 44 'fi PANEL 300 RECORD 350- I BUTTON 340 I 374 I /368 R HEAD 1 EI AY TRANSFERCONTROL. SELECTOR SYSTEM 350 370 Q l I MEMORY GATE so BIT SHIFT REGISTER]: DRuM m, D I

L 376 g l 364 f 362 START 359 SHIFT PULSE W PULSES FORMING AMPL' STOP 35! HEAD TIMING I E E211 l 353 I M135 1 PROGRAM I FIG 6 SELECTOR-360 c sum as or 13 PAIENTEDIIII 91972 l I I I I I I I I I I I I I I .I

A PATENTEUMM sum UB'UF 13 310 E3400 402 OUT-IN -5 I ENCODER EIO D404 8 324 I El WRIST SWIVEL ENCODER 5 V Elo 40s 7 v 314 T E 408 I 420 4l8 DOWN'UP GRAEAOJEINARY ENCODER l E 410 l3 CONVERTER El WRIST BEND E2 4|2 1 ENCODER E" 4 4 SiMiriEiDfl/E 326 T f El ROTARY I I ENCODER E5 422 I COMPARATOR 2 435 (SUBTRACTION BY L. gl 'COMPLIMENT RY 424. T- A 434 I ADDITION) '3 OUT-IN Y O COMMAND I FINAL 7 FROM REGISTER 392 I CARRY 454 426 I WRIST SWIVEL I COMMAND l DOwN-uP COMMAND GRAY m BINARY FROM REGISTER 392 FROM REGISTER 392 COFOSEERTER 430 Al 45/0 WRIST BEND A2 442 1 COMMAND 444 FROM REGISTER 392 E A ROTARY COMMAND PAIENTEDMAY 91972 sum in nr 13 NNTmEEEES 205 Y R R A c L A W F PAIENTEIIIII 9m 3,661,051

SHEET 12 0F. 13

FIG 13 HYDRAU LIC SUPPLY PROGRAM ONE PROGRAM Two PROGRAM THREE INTERVAL INTERVAL INTERVAL l ONE DRUM REVOLUTION 354 354 L *1 WORD ONE TRACK W 5 WORD Two TRACK K WORD THREE TRACK 358 lllllll llllll llllllllllllll lllllllljllll CLOCKTRACK +-eo PULSES-J L ao PuLsEs 80 PULSES FIG. 14

PROGRAMMED MANIPULATOR APPARATUS This is a continuation application of application, Ser. No. 808,152 filed Mar. 18, 1969, now abandoned.

The present invention relates to manipulator apparatus,

in general, been satisfactory for their intended purpose, they have nevertheless suffered from a number of disadvantages. Thus, up to the present time, the cost of programmed manipulator apparatus has been such as to limit the widespread usage of such devices. Furthermore, the prior art arrangements lack flexibility in maneuvering of the programmed manipulator arm. In addition, movement of the manipulator arm in the controlled axes has been relatively slow and, in many instances, involved abrupt accelerations and decelerations of the arm which produce excessive wear and shock on the apparatus. Furthermore, the time required to perform a given series of operations was quite large due to the fact that the manipulator arm had to be brought to a halt between each programmed step, or group of steps.

It is, therefore, a primary object of the present invention to provide a new and improved programmed manipulator ap-v paratus which avoids one or more of the above-described disadvantages of prior art arrangements.

It is another object of the present invention to provide a new and improved programmed manipulator apparatus which may be manufactured on a mass production basis at low cost and with improved performance.

It is a further object of the present invention to provide a new and improved programmed manipulator apparatus wherein a low cost hydraulic system-is incorporated to move the manipulator arm in all controlled axes.

It is another object of the present invention to provide a new and improved programmed manipulator apparatus wherein the manipulator arm may be moved at high velocity and without halting at programmed points so as to decrease substantially the time required to perform a given series of movements.

It is a further object of the present invention to provide a programmed manipulator apparatus in which the manipulator arm is controlled from point to point information while providing effectively continuous path movement of the manipulator arm.

It is a still fu'rther'object of the present invention to provide a programmed manipulator apparatus which employs a simplified electronic control system in which a single comparator and digital analog converter is employed for all controlled axes of the apparatus.

It is another object of the present invention to provide a,

programmed manipulator apparatus wherein acceleration and deceleration of the manipulator arm in each controlled axis is accomplished at a maximum value without exceeding predetermined design limits of the apparatus.

Briefly considered, the programmed manipulator apparatus of the present invention employs a continuously rotating memory drum in which may be stored signals representing a number of steps in a desired sequence of operations. A portable teach control assembly is employed during the teaching operation to establish each desired position of the manipulator arm which is then recorded on the memory drum. During repeat operation, command signals derivedfrom the drum are compared with accurately produced encoder signals and the manipulator arm is moved to each set of positions as called for on the drum. The manipulator arm may either be made to move to the programmed point exactly, or movement of the arm may be made on a continuous path basis, and over curved paths, by employing artificial coincidence signals which may be developed while large error signals still exist in the controlled axes. As a result, time required to perform a given series of operations is substantially increased.

A common comparator and digital to analog converter is employed to control all axes of the apparatus while providing coincidence signals representing different magnitudes of error signals. The output of the digital to analog converter is correlated with the apparatus used to move the manipulator arm in each axis so that maximum acceleration and deceleration can be produced without exceeding the design limits of the apparatus.

The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the following specification taken in connection with the accompanying drawings, in which:

FIG. 1 is a perspective view of a programmed manipulator apparatus embodying the features of the present invention, taken from the right-hand side thereof;

FIG. 2 is a perspective view of the apparatus of FIG. 1 but taken from the left-hand side thereof;

FIGS. 3 and 4, when assembled in the manner shown in FIG. 4A, constitute aschematic diagram of the hydraulic and pneumatic components of the apparatus of FIG. 1;

FIG. 5 is a basic block diagram of the electronic control portion of the apparatus of FIG. 1, illustrated in conjunction with a single controlled axis thereof;

FIG. 6 is a block diagram of the control system of the apparatus of FIG. 1 when operated in the teach mode and illustrating the manner in which information from all five axes of the apparatus are recorded on the memory drum during the teach mode;

FIG. 7 is a block diagram of the control system of the apparatus of FIG. 1 when operated in the repeat mode and shown in conjunction with all five axes of movement of the apparatus of FIG. 1;

FIGS. 8 and 9,.when arranged in the manner shown in FIG. 9A, comprise a block diagram of the multiplex comparator system employed in the control system of the apparatus of FIG. 1;

FIGS. l0, l1 and 12, when arranged in the manner shown in FIG. 12A, comprise a schematic diagram of the digital to analog converter and certain control circuits of the control system of the apparatus of FIG. 1;

FIG. 13 is a sectional view of the servo valve arrangement employed to actuate eachof the hydraulic cylinders in the manipulator apparatus of-FIG. l;

FIG. 14 is a timing diagram illustrating the manner in which different programs may be recorded on the memory drum portion of the control system of the apparatus of FIG 1;

FIG. 15 is a graph illustrating one mode of operation of the manipulator arm of the apparatus of FIG. 1;

FIG. 16 is a diagrammatic view of a preferred characteristic of the servo valve of FIG. 13;

FIG. 17 is a graph of the current-flow characteristic of the servo valve of FIG. 13;

FIG. 18 comprises two graphs useful in explaining the deceleration characteristic of the apparatus of FIG. 1';

FIG. 19 is a right-side view of a portable teach control assembly used in conjunction with the apparatus of FIG. I during the teaching mode;

FIG. 20 is a top view of the teach control assembly of FIG. 19; and

FIG. 21 is a front view of the teach control assembly of FIG. 19.

Referring now to the drawings, and more particularly to FIGS. 1 to 4, inclusive, thereof, the programmed manipulator apparatus of the present invention is therein illustrated as comprising a generally rectangular base or mounting platform 40 on which the hydraulically powered manipulator arm of the apparatus is supported together with all of the hydraulic, electrical and electronic components necessary to provide a five programmed articulations or degrees of freedom for the manipulator arm.

Specifically, the base 40 supports a control cabinet indicated generally at 42 within which is housed the electronic control system portion of the manipulator apparatus, said cabinet having a control panel 44 on which are located the variouscontrols of the control system necessary to control movement of the hydraulically powered manipulator arm in both an initial so-called teaching mode and in a repeat mode in which the manipulator arm is moved in repetitive cycles through a sequence of movements in each of the five axes as programmed during the teaching operation.

The hydraulically powered manipulator arm comprises a boom assembly indicated generally at 50, which is pivotally mounted for movement about a horizontal axis by means of a pair of ear portions 52 and 54 which are pivotally mounted on the outboard side of a pair of upstanding opposed ear portions 56 and 58 of a hollow trunk portion 60 which is rotatably mounted on a hollow, fixed, vertically extending column 61 the bottom portion 62 of which is secured to the platform 40. The ear portions 52, 54 are mounted on stub axles 316 which project outwardly from the trunk ears 56, 58 so that the boom assembly is supported at points which are spaced relatively far apart so as to provide maximum resistance to torsional forces tending, to twist the boom assembly 50 about its longitudinal axis.

The boom assembly 50 is tilted to give a down-up motion of the outer end of the manipulator arm by means of a down-up hydraulic cylinder 64 the bottom end of which is pivotally mounted in a block 66 secured to the bottom edge portion of the trunk 60, the movable plunger portion 68a of the cylinder 64 being pivotally secured to the boom assembly 50 forwardly of the trunk 60 so that movement of the piston 68a causes the boom assembly 50 to pivot about the pivotal axis of the ear portions 56 and 58. In order to prevent excessive error in positioning the manipulator arm in down-up axis, particularly when the boom 50 is extended and is carrying a heavy load, the trunk 60 is journaled in bearings 63 and 65 located at the bottom and top, respectively, of the fixed column 61. With this arrangement, the block 66 which mounts the lower end of the hydraulic cylinder 64 is located over the bearing 63 and side thrust developed by the cylinder 64 is transmitted directly to the fixed column 61 so that tilting of the trunk 60 about the vertical axis is avoided. As a result, the outer end of the boom assembly may be accurately positioned at full extension and maximum load.

The boom assembly 50 includes a pair of hollow extendable arm portions 68 and 70 which are arranged to be moved as a unit in and out of the corresponding portions of the boom assembly 50 by means of a hydraulic cylinder 72 which is positioned between the arm portions 68, 70 and provides a socalled radial extension or retraction of the manipulator arm. More particularly, the outer ends of the tubes 68, 70 are secured to a crosshead assembly 74 and the extendable long stroke piston 76 of the cylinder 72 is pivotally connected to the crosshead assembly 74 intermediate the arm portions 68, 70.

The crosshead assembly 74 carries a forwardly projecting hand portion 78 to which is connected a pneumatically operated clamping device indicated generally at 80, commonly called a hand assembly, which is provided with opposed grasping fingers 82, 84 arranged to support any desired object 86.

The hand assembly 80 is arranged to be moved in two different axes independently of movement of the boom assembly 50. More particularly, the member 78 is arranged to be rotated about the pivotal axis 88 of the crosshead assembly 74, this movement being referred to as wrist bend or simply bend.

In addition, the member 78 is arranged to be rotated about its longitudinal axis so as to produce a rotation of the hand assembly 80 about the central longitudinal axis of the boom assembly 50, this motion being referred to as wrist swivel or simply swivel.

In order to produce bending motion of the hand assembly 80, there is provided a hydrualic cylinder 90 which is mounted along the left-hand side of the boom assembly 50 and is provided with a double ended piston-type plunger 92. The ends of the plunger 92 are interconnected through a roller chain 94 which extends over a pair of sprockets 96, so that linear movement of the double ended plunger 92 is translated into rotational movement of beveled gears 98 which in turn cause rotation of a torque tube which contains a ball-nut in the outer end thereof near the forward end of the boom assembly 50. This ball-nut is slidably engaged with a spline shaft carried within the arm portion 68 which is free to move into and out of the torque tube as the arm portion 68 is extended and retracted.

Rotation of this spline shaft is then transferred by means of bevel gears in the crosshead assembly 74 into a bend motion of the member 78 about the axis 88.

In a similar manner a hydraulic cylinder 100 is mounted on the right-hand side of the boom assembly 50 and is provided with a double-ended piston plunger 102, the ends of which are interconnected by means of a roller chain 104 extending around sprockets 106 also mounted on the right-hand side of boom assembly 50. Rotation of the rear sprocket 106 causes rotation of beveled gears 108 which in turn produce rotation of a second torque tube having a similar ball-nut at the forward end thereof so that a spline shaft which is slidably engaged with the ball-nut is rotated in response to motion of the swivel plunger 102. Rotation of this spline shaft is then translated by means of beveled gears in the crosshead assembly 74 into rotary motion of the member 78 so as to produce the desired wrist swivel action of the hand assembly 80.

The fifth degree of freedom comprises a rotary motion of the entire boom assembly 50 about the vertical axis of the trunk 60. In order to provide a positive drive for the trunk 60 so that the boom assembly 50 may be accurately positioned in rotary motion and may be rapidly decelerated to the desired end point, a ring gear is mounted on the bottom end of the trunk 60 and engages a rack 122 the ends of which are arranged to be connected to the plungers of a left-hand hydraulic cylinder 124 and a right-hand hydraulic cylinder 126.

Accurate positioning of the boom assembly 50 in rotary movement is assured by means of a backlash control cylinder 128 which is provided with a piston having an end button 130 which protrudes from the cylinder and slidably engages the back side of the steel rack 122. System hydraulic pressure is supplied to the cylinder 128 so that the button 130 urges the rack 122 into engagement with the ring gear 120 with a force which is somewhat greater than the maximum separating forces experienced under maximum acceleration or deceleration conditions of the boom assembly 50. The hydraulic cylinders 124 and 126 are mechanically adjusted by means of the screws 132 so that the housings thereof are centered about the line of motion of the rack 122 and the plungers of the respective cylinders. In order to reduce wear on the backlash piston button 130, this button is preferably made of bronze filled teflon. This material has been found to have superior wear characteristics over either an all bronze piston which would have high friction and would wear out quickly or a pure teflon button which would have a tendency to cold flow under the pressure exerted by the cylinder 128.

Hydraulic power for the operation of the above described hydraulic cylinders is provided by a completely self-contained hydraulic system mounted on the base platform 40. Basic hydraulic power is generated by a gear-type pump which is driven by an electric motor 142. Hydraulic fluid, at atmospheric pressure, flows from a reservoir 144 to the inlet of the pump 140. The output of the pump 140 flows through a ten micron filter 146 to a base manifold 148 which is mounted on the platform 40. An unloading valve 150 in the base manifold 148 acts automatically to maintain an average system pressure of approximately 850 psi. Under low flow demand, the output of the pump 140 is returned to the reservoir 144 directly over the hydraulic return line 152. Under high flow demand, pump output is directed to the system hydraulic cylinders. A dump valve 154 is provided in the base manifold 148 which can be used to reduce system pressure to zero. A check valve 156 is provided at the output of the unloading valve 150 to prevent reverse flow of fluid when the pump 140 is operating under low flow demand or when it is not operating at all.

The output of the unloading valve 150 is directed to an accumulatoi' 160, a pressure switch'l62, a pressure gauge 164, and the five servo valves which are employed to control the above-described hydraulic cylinders which move the arm and hand assembly in the desired five degreesof movement, these servo valves being individually controlled by electrical signals developed in the control system portion of the manipulator apparatus, as will be described in more detail hereinafter. Specifically, a rotary servo valve 166 is mounted on the platform 40 and is arranged to supply controlled hydraulic fluid to the cylinder 124 over the conduit 168 and to the cylinder 126 over the conduit 170. Hydraulic fluid at system pressure is also supplied over the conduit 169 through the hollow trunk column support 61 to a trunk through-feed assembly which provides a path for the flow of pressure and return fluid from the stationary base assembly to the rotating boom assembly 50. The through feed assembly comprises a stationary tube within a concentric passage in a trunk feed-through manifold 171 which moves with the boom 50. Fluid'at system pressure is directed to the tube of the through feed assembly, through the manifold 171 at the top of the trunk 60 and from there directly to the forward end of the out-in cylinder 72 over a conduit 172. System pressure is also supplied to the pressure port of a down-up servo valve 174 which is mounted on and rotatable with the trunk 60, the down-up servo valve 174 being arranged to supply controlled pressure to either end of the hydraulic cylinder 64 over the conduits 176 and 178. The feed-through manifold 171 also supplies system pressure to a boom manifold 180 which is mounted on and is rotatable with the boom assembly 50. The boom manifold directs fluid at system pressure to the pressure port of an out-in servo valve 182 which is mounted on the rear end of the boom assembly 50, a bend servo valve 184 which is mounted on the left-hand side of the boom assembly 50 beneath the bend cylinder 90, and a swivel servo valve 186 which is mounted on the righthand side of the boom assembly 50.

The out-in servo valve 182 supplies controlled pressure over the conduit 190 to the rear end of the out-in hydraulic cylinder 72, and fluid at system pressure is admitted to the rod side of the piston 76 over the conduit 172 at all times. The differential piston area thus provided in the cylinder 72 permits cylinder operation over a long stroke and at a reduced net flow requirement. Accordingly, as the piston 76 is moved forwardly fluid is returned over the conduit 172 to the servo valve 182 and recirculates to the piston side of the cylinder. However, the area of the rod side of the piston is made equal to one-half the area of the piston and the volume of flow into the conduit 172 is one-half that of the controlled flow from the valve 182. As a result, the force which is available from the cylinder 72 is lower than system pressure but approximately equal velocity of the piston 76 in both directions is thereby provided.

The bend servo valve 184 supplies controlled pressure to the hydraulic cylinder 90 over the conduits 192 and 194 and the swivel servo valve supplies controlled pressure to the cylinder 100 over the conduits 196 and 198. The servo valves 166, 174, 184 and 186 each act to direct fluid under pressure to one side of the hydraulic cylinder and open the opposite side of the cylinder for return flow over the indicated return conduit 200. With regard to the rotation cylinders, fluid is admitted and returned from the piston side of each actuator so that the two pistons of the cylinders 124 and 126 and the rack 122 act as a single piston in a single cylinder.

' A pair of relief valves 202 and 204 are connected across the output of the rotary servo valve 166 and act to direct excessive pressure to the return line 200 so as to improve the deceleration characteristics of the boom assembly 50 in rotary motion and to eliminate shock loads on the rack 122 and ring gear 120. The relief valves 202 and 204 are arranged to be mounted as cartridge inserts in the side of the manifold 148 for easy servicing and replacement. A pair of relief valves 206 and 208 are also connected across the output of the bend servo valve 194 and a pair of relief valves 210 and 212 are connected across the output of the swivel servo valve 186 to provide protection for the respective bend and swivel drive trains in case the hand assembly strikes an obstacle or is overlaoded. The relief valves 206, 208 and 210, 212 are likewise mounted as cartridge units on the side of the boom manifold 180.

Return lines for the down-up servo valve 174 and boom manifold 180 carry returnfluid to the trunk feed through manifold 171 and thence to the return passage within the column 61. This return fluid flows to the base manifold 148, over the return conduit 152 and through a heat exchanger 214 to the reservoir 144. A heat exchanger fan 2l6 is driven directly by the motor 142 and a 5-micron filter 218 is connected across the heat exchanger to provide additional fluid filtering. Flow through the filter 218 is based on pressure drop across the heat exchanger and is, therefore, only partial flow.

The accumulator is charged with dry nitrogen to 575 p.s.i. and assures that system pressure will be maintained when flow demands exceed the output flow capacity of the pump 140. The normally open contacts of the pressure switch 162 are closed whenever system pressure is above 300 p.s.i. The contacts of the switch 162 are connected into the control circuit for the motor 142 and are arranged to turn off the manipulator apparatus whenever system pressure drops below 300 p.s.i.

Compressed air for operation of the hand clamp is supplied through a regulator 230, a flexible hose 232 to the boom assembly 50, and through an in-line lubricator 234 to the pressure port of a three-way solenoid valve 236. The lubricator 234 introduces a measured amount of oil according to air flow for lubrication of the working parts of the air system. The controlled port of the solenoid valve 236 supplies controlled air through a telescoping air line 238 and a swivel fitting 240 to the hand air cylinder while permitting boom and hand motions. When the solenoid 236 is de-energized, pressure air is connected to thehand cylinder causing the fingers 82, 84 to close. When the solenoid 236 is energized the solenoid pressure port is closed, the hand cylinder is connected to exhaust and the hand is spring urged to an open position.

Each of the servo valves 166, 174, 182, 184 and 186 is a four-way, infinite-position valve which is responsive to both the polarity and amplitude of a direct current signal developed in the control system portion of the apparatus. Direction of motion of the pilot spool in each servo valve is determined by the polarity of the incoming electrical signal and the magnitude of this signal determines how far the valve will Open and therefore how fast the controlled hydraulic actuator will move. Preferably, these servo valves are actuated by a long stroke electromagnetic actuator mechanism which is positioned in line with the pilot spool of the servo valve to provide fast response of the servo valve and its associated hydraulic cylinder to the incoming electrical signal on a hydraulic feedback basis and without requiring mechanical linkages for feedback to the input, as will be described in more detail hereinafter.

Considering now the control system portion of the man ipulator apparatus, reference is made to FIG. 5 wherein the basic components of the control system are shown in block diagramform in conjunction with one controlled axis, the out-in axis, of the manipulator apparatus. The control system includes a continuously rotating memory drum 300 in which digital information may be stored relative to three different programs each consisting of a number of program steps up to a maximum of 60 steps in each program. The control system of the manipulator apparatus has two basic modes of operation. The first mode is a so-called teach mode in which the hydraulically powered manipulator arm is moved to the series of successive positions to which the arm is to be successively moved during repetitive working or repeat cycles. Each time that the manipulator arm is moved to a new position this position is recorded on the memory drum 300, together with associated auxiliary signals relating to how that particular program step is to be carried out. Tothis end, a pair of teach-repeat switches 302, 304 are provided. When the switches 302, 304 are thrown to the teach position, the teach control circuits 306 are connected to the input of the servo amplifier 308 which controls the out-in servo valve 182.

The teach control circuits 306 include suitable voltage sources for moving the manipulator arm in all five axes, as well as controls relative to the accuracy with which the arm is to be moved to the desired position, the operation of the hand clamp air cylinder, and other functions, as will be described in more detail hereinafter. The signal supplied to the out-in servo amplifier 308 opens the valve 182 by an amount determined by the amplitude of this signal so that the hydraulic cylinder 72 moves the hand assembly in the desired direction along the out-in axis. For purposes of illustration, the servo valve 182 is shown in FIG. as having bi-directional outputs to the out-in hydraulic cylinder 72. However, it will be understood that with reference to the particular cylinder 72, the rod side of the cylinder is supplied with system pressure rather than through the servo valve 182, as has been described in more detail heretofore. The resulting pressure on the piston of the cylinder 72 moves the hand assembly 80 in or out, depending upon the polarity of the electrical signal developed by the teach control circuit 306.

In order to provide digital information representing the absolute position of the arm and hand assembly in each of the five controlled axes of movement thereof, there is provided a series of digital encoders, one for each controlled axis. More particularly, an out-in encoder 310 is mounted at the rear end of the boom assembly 50, behind the hydraulic cylinder 72 and is mechanically interconnected with the crosshead assembly 74 by means of a follow up linkage 312 so that as the hand assembly 80 is moved along the radial or out-in axis a digital signal is developed by the encoder 310 which represents the absolute position of the hand assembly in this axis in digital form. In a similar manner a digital down-up encoder 314 is provided to develop an absolute position signal which changes in a digital manner in response to tilting of the boom assembly 50 about the fixed axle 316 on which the ear portion 54 is rotatably mounted. The encoder 314 is mounted on the end of the axle 316 through an intermediatemember 318 and is driven from a large spur gear 320 which is mounted on the ear portion 54 of the boom assembly 50 and moves therewith. Accordingly, as the boom 50 is tilted about the axle 316 the gear 320 rotates and through an intermediate gear drives the encoder 314 so that the desired absolute position signal is obtained in the output thereof.

A bend encoder 322 is mounted on the left-hand side of the boom assembly and is driven from the gearing 98 associated with the hydraulic cylinder 90 so as to develop a digital output signal corresponding to the position of the cylinder 90 and hence the position of the hand assembly 80 in the wrist bend axis. A wrist swivel encoder 324 is mounted on the right-hand side of the boom assembly 50 and is mechanically interconnected with the gearing associated with the hydraulic cylinder 100 so as to provide a digital output signal corresponding to movement in the wrist bend axis. A rotary encoder 326 is mounted on a stationary bracket portion 328 of the base assembly 62 and is interconnected with the rotatable trunk assembly 60 through a chain and sprocket drive so that a digital output signal is developed by the encoder 326 representing the absolute position of the boom assembly 50in rotary movement of the trunk 60 about a vertical axis.

Each of the encoders 310, 314, 322, 324 and 326 is preferably of the type shown in a copending application of George Hamlin Leonard Ser. No. 494,524, filed Oct. 11,.

1965, in order to provide a high degree of accuracy of the digital information developed by the encoder while at the same time providing for relatively long distances of travel in each of the five controlled axes. While reference may be had to said copending Leonard application for a complete and detailed description of such encoders, it may be stated generally that such an encoder comprises a pair of code-bearing discs which are geared together so as to advance continuously at different ratios in accordance with the mechanical input signal. The successive code combinations of the two discs are continuously sensed, each code member contributing its part to a composite code combination. The high speed code member rotates one revolution in the course of a single codecombination advance of the low speed code member. An arrangement is provided for insuring accurate transfer of information from one bit to the next on the low speed disc during a change in the high speed code member from one code bit at the completion of one code cycle to the next code bit at the start of the next code cycle. By employing combinational codes derived from both high speed and low speed discs, large digital numbers and hence large distances of movement in each axis may be measured by the encoders, while providing high accuracy digitized output signals. The encoder for a particular axis will develop a digital signal having a number of digits corresponding to the movement which is to be made in that axis and the degree of accuracy required therein. For example, the encoder 310 may develop a 10-bit digital signal, the encoder 324 may also develop a ten bit signal, the encoders 314 and 322 may develop 1 l-bit digital signals, and the rotary encoders 326 may develop a 13-bit digital signal. Such encoders have been found suitable for movement of the manipulator arm a distance of 42 inches in the out-in direction, a wrist swivel travel of 320, a down-up movement corresponding to a tilt to the boom assembly from 27 below horizontal to 30 above horizontal, a wrist bend traverse of 220 centered about a horizontal axis, and a rotary movement of the trunk 60 of 220.

Referring again to the teach mode of operation of the control system, when the hand assembly has been moved to the desired position, the encoder 310 continues to develop a digital output signal representing this final position of the hand assembly in the out-in axis. The manipulator arm and hand assembly is also positioned in the other four axes of movement so that the hand assembly is in a desired final position and orientation to which it is to be moved during a repeat cycle. The digital signals which are continuously produced by the encoders associated with each axis are supplied through the switch 302 to one side of a normally open record button'340. In addition, certain other signals are supplied to the record button 340 from the teach control circuits 306, and also from the control system as set up on the control panel 44, which indicate other functions which are to be be performed in conjunction with movement of the manipulator arm to the desired position. The record button 340 is then depressed and supplies all of these signals to the memory drum 300, so that the information represented thereby is recorded on the memory drum 300 at a desired position corresponding to the particular program step which is being taught. Preferably, the digital signals which are developed by the encoders such as the encoder 310, are in reflected binary code, as distinguished from standard binary code, for the reason that the reflected binary signal is one in which only one digit changes between successive numbers in the code.

After the record button 340 is released the teach control circuits 306 are actuated so as to move the hand assembly 80 to a new position by energization of those ones of the hydraulic cylinders in each axis which must be changed from the previously programmed position. When the next position is reached, the record button is again depressed so as to record the new digital information for each axis at the new program step area of the memory drum 300. This sequence of operations is carried out until the manipulator arm has been moved to the last desired position at which point an end of program bit is recorded in the memory drum 300 along with information relating to the last program step.

After a complete program consisting of a number of positions to which the manipulator hadn is to be moved in succession has been recorded in the memory drum 300, the repeat teach switches 302 and 304 are thrown to the repeat position.

the memory drum command signal and derives both a direction signal signifying the direction in which the hand should be moved to reduce the error, and a distance signal corresponding to the difi'erence between the encoder signal representing the actual position of the hand assembly 80 and the desired position as stored in the memory drum. In the illustra'ted out-in axis, these signals are supplied by way of the switch 304 to the servo amplifier 308 whichcontrols the servo valve 182 so that the cylinder 72 moves the hand assembly in the correct direction to reduce the error signal to zero or to some programmed magnitude of error signal. When final coincidence is obtained in. all axes of the apparatus, the next programmed step is read from the memory drum 300, is compared with the various encoders in each axis and the corresponding error signals are employed to drive the corresponding hydraulic cylinders to the next programmed point in each axis. When the manipulator arm is moved to the last programmed position the end of program bit is employed to restart the programmed series of operations so that the manipulator arm repetitively moves through the taught series of motions during repetitive work cycles and until the apparatus isturned off.

Referring now to FIG. 6, the control system of the manipulator apparatus is shown therein in somewhat more detailed block diagram form in conjunction with all five axes of movement and illustrates the manner inwhich the memory drum is programmed during the teaching mode of operation. The memory drum300 is provided with a series of 60 read-write heads 350 which are spaced along the length of the memory drum 300 and may be employed as either write heads during the teaching operation or'as read heads during the repeat mode of operation of the apparatus. In order to increase the versatility of the manipulator apparatus, the memory drum 300 is arranged so that three different programs may be stored within the memory drum 300, any one of these programs being selected from the control panel 44 of the apparatus in accordance with a master control program or by manual selection. More specifically, the periphery of the drum is divided in the manner shown in FIG. 14 so that a program one interval is provided for the first third of a drum revolution, a program two interval is provided during the second third and a program three interval during the final third of each drum revolution. The endpoints of each of the program intervals are defined by wordtracks which are permanently recorded in the memory drum 300 and'occur once each revolution at the desired staggered intervals to define the desired program intervals. A series of three timing heads 351, 352 and 353 are provided to sense these word tracks, the timing head 351 detecting the word one track pulses 354 (FIG. 14) the head 352 detecting the word two pulses 355 and the head 353 detecting the word three pulses 356. The outputs of the heads 351, 352 and 353 are supplied to a program selector 360 so as to control the start and stop points of a particular program interval. For example, the timing pulses 354 define the start of the program one interval and the pulses 355 define the end of this interval. During the first program interval clock pulses 358, which are detected by a clock head 359 are selectively supplied to an amplifier 362, the start and stop pulses derived from the program selector 360 being employed to prevent further clock pulses derived from the clock track from appearing in the output of the amplifier 362 during the second and third program intervals.

The clock pulses which are selectively transmitted to the amplifier 362 are supplied to a pulse forming circuit 364 and are then employed as shift pulses which are supplied to an 80- bit shift register 366. In the illustrated embodiment, each program interval includes 80 clock pulses so that 80 bits of information may be recorded along one-third of the periphery of the memory drum 300 during one step of a particular selected program interval. The encoders 310 and 324 associated with the out-in and swivel axes develop 10-bit code numbers, the encoders 314 and 322 associated with the down-up and bend axes develop ll-bit numbers, and the rotary encoder 326 develops a 13-bit number. Accordingly, 55 information bits are required to record all five positions of these encoders. In addition, other auxiliary functions may be selected by the teach control circuits and the control panel 44 and recorded in the memory drum at a particular program step so as to cause the manipulator apparatus to perform auxiliary functions in conjunction with a particular step. For example, a bit designating that the manipulator shall move at a slow speed to the programmed end point may be recorded. Bits representing different accuracies with which the manipulator is to be moved to the designated end points may be recorded, a bit indicating actuation of the hand clamping device, or a bit indicating the end of a particular program may also be recorded. Also, a number of other bits may be recorded for various optional types of operation of the manipulator apparatus with other apparatus, including interlock circuits, and the like. For example, a desired operation may require either that the manipulator apparatus develop an operate external (OX) signal at a particular program step, which is supplied to external apparatus to actuate a particular device, or in the alternative that the manipulator apparatus wait until a wait external" signal (WX) is received from an external apparatus indicating that some particular auxiliary operation has been performed. A number of additional storage bits are thus available in the -bit shift register 366 for such options.

Considering now the actual operation of the manipulator apparatus in recording a particular program step during a teaching operation, the teach controls 306 are illustrated in FIG. 6 as individually comprising plus and minus variable voltage sources indicated generally by the potentiometers 370a and 372a which may be selectively supplied to the servo amplifier and servo valve of a particular axis through separate push buttons. For example, the teach controls of the out-in axis 374a comprise an out push button 376a which, when depressed, supplies a positive, voltage to the out-in servo amplifier and servo valve indicated by the block 378. In a similar manner an in button 380 may be depressed and supplies a negative voltage to the servo amplifier 378. As described previously, the servo valves of the respective axes respond to the electrical signals developed during the teaching operation by moving the corresponding hydraulic cylinders and the consequent movement in the particular axis is also operative to move the corresponding encoder a proportionate amount. Therefore, as a result of the teaching operation in the out-in axis, the hand'assembly is moved to a desired position which is thereafter continuously represented by the digital output of the out-in encoder 310. Similar teach controls 382, 384, 386 and 388 are provided for controlling movement in the swivel, down-up, bend and rotary axes and the push buttons in these respective controls are selectively depressed by the operator for a length of time sufficient to move the hand assembly to the new position in each of the five controlled axes. Preferably, the voltages developed by the teach controls 306 are of relatively small amplitude so that the manipulator arm is moved relatively slowly in each axis thereby facilitating the exact positioning of the arm at the desired position in each axis by the operator. The teach controls 306 as well as the record button 340 and certain other controls, are contained in a portable teach control assembly which is interconnected with the cabinet 42 of the apparatus by means of a flexible cable so that the operator can move to any desired position during the teaching operation and control the recording steps remotely, as will be described in more detail hereinafter.

When the arm and hand assembly has been precisely positioned in each axis and the desired auxiliary functions described above, as well as any desired options, have been set up in the transfer control apparatus 368, the record button 340 is depressed and all of the encoder output signals, auxiliary signals and option signals are transferred in parallel to the 80-bit shift register 366. When this transfer is completed, a signal is supplied to an input gate circuit 370 which permits shift pulses to be applied to the 80-bit shift register 366 so that the digital information which has been transferred to the register 366 is serially supplied through a write amplifier 372 to a particular one of the read heads 350 under the control of a relay selector system 374. Assuming that the selector system 374 is set to supply the recording signal to the first one of the heads 350, the first step in the selected program interval will then be recorded on the memory drum 300. The final output from the shift register 366 is then supplied over the conductor 376 toturn off the gate 370. The end of register pulse is also supplied to the selector system 374 so as to cause the write amplifier 372 to be connected to the next one of the heads 350.

In asimilar manner, the teach controls 306 are again selectively actuated to bring the hand assembly 80 to a new position so that new digital information is available from each encoder and this information is again recorded as the second step in the selected program by depressing the record button 340. It will thus be evident that a series of up to 60 program steps may be recorded during a particular program interval, each of these program steps including the absolute position to which the hand assembly is to be moved in each axis, the speed at which such movement is to take place, the accuracy with which positioning is to be accomplished, the actuation of the hand clamping device, and finally in association with the last program step an indication that the end of the program has been reached and that the relay selector system 374 should be reset to the first program step and the cycle repeated. In this connection it should be noted that the program selector 360 and the relay selector system 374 may be controlled by proper interconnections, to provide other combinations than three programs having 60 steps each. For example, the units 360 and 374 may be interconnected to provide a single program having 180 steps which is repeated during repetitive work cycles, as will be readily understood by those skilled in the art.

IN FIG. 7 the operation of the manipulator apparatus in the repeat mode of operation is shown in more detailed block diagram form and in conjunction with all five axes of movement. Referring to this figure, it is assumed that the relay selector system 374 is connected to the first one of the heads 350 which is used as a read head during the repeat operation. The output of this head is sent to a group of control circuits indicated generally at 380 wherein the clock and word tracks are employed to select the desired program interval and the programmed bits of information corresponding to the first recorded step of the selected program. These programmed bits are supplied over the conductor 382 to a sense amplifier 384 from which they are supplied to the 80-bit shift register 366. After the first program step information has been read into the register 366 a signal is supplied over the conductor 386 to the control circuit 380 which respond by sending a control signal over the conductor 388 to a parallel transfer circuit 390 which is interconnected between the 80-bit shift register 366 and an 80-bit buffer storage register 382 on an individual basis for each bit. Parallel transfer circuit 390 then transfers the 80 bits of information in parallel to the 80-bit buffer storage register 392 wherein they are stored until the arm and hand assembly has been moved to the position designated by the position signals stored therein. The position signals stored in the register 392 and representing the desired end points of the program step in each of the five axes, are supplied to a multiplex form of comparing arrangement indicated generally at 394 wherein the encoder signal is compared with the digital command or position signal stored in the register 392 and develops a digital error signal. This digital error signal is converted to an analog voltage which is then demultiplexed and stored both as to direction and distance, these stored signals then being supplied to the individual servo valves corresponding to each axis. The respective servo valves then function to move the corresponding hydraulic cylinder so that the encoders are moved in the direction to reduce the error signal to zero in each axis.

While this motion is taking place, the relay selector system 374 is shifted to the next read head 350 and the second step information is read into the shift register 366. When total coincidence is achieved in all five axes, a signal is developed on the conductor 396 which is supplied to the control circuits 380 which respond by sending a control signal to the parallel transfer circuits 390 over the conductor 388.,The parallel transfer circuits 390 then transfer in parallel the bits of information from the shift register 366 to the buffer storage register 392. The information thus stored in the register 392 becomes the new command signals for controlling the servo systems in each axis. At the same time, the relay system 374 is stepped to the next head 350 and the third step information is read into the shift register 366. I

In this manner the hand and arm assembly is moved to the respective positions which have been programmed into the memory drum during the teaching operation. When a program step is encountered which includes an end of program bit, this information is supplied to the control circuit 380 over the conductor 398 which respond by resetting the relay selector system 374 to the first programmed step, as well as performing other auxiliary control functions necessary to repeat the recorded program.

In connection with the recording of information on the memory drum 300 during the teaching mode, and the reading out of information during the repeat mode, it is pointed out that if the recording is of the type in which the direction of current in the write head is directly determined by the binary character of the data fed in, i.e., the non-return to zero type of recording, the direction of the current changes only when the binary character changes. Thus, with such a recording system a word consisting of all binary ONE or all binary ZERO digits has no current reversals in it. Accordingly, when such recorded data is sensed, the head output is zero during the entire binary number, since, with no current reversals there are no flux reversals, and therefore no signal is induced in the read head. Such a recording system is sensitive to error in that any noise or pickup which occurs may change the binary sense of a triggered bistable or flip-flop stage so that all succeeding information data would be incorrect since there would be no corrective output from the read head. Also, residual data on any drum track due to previous recordings which are not properly erased by application of unidirectional current, may be large enough to cause the sense amplifier to trip thus giving an incorrect final output.

In order to overcome these difficulties, the memory drum control circuits 380 preferably employ a system known as phase modulated recording which system has the characteristic that every bit of data, regardless of its binary sense, must include an induced output from the read head, and therefore must have included a current reversal when recorded. The phase modulated system of recording also has the characteristic that the binary sense of the data must be uniquely related to the polarity of the head output.

In such a phase modulated recording system, the clock system is so arranged that not only are the regularly spaced clock pulses 358 available, but also a second signal is available which divides the time interval between clock pulses into first half and second half periods. During the first half period, a binary ONE data input must produce positive current in the write head, and during the second half period, it must produce negative current in the head. Similarly, during the first half period a binary data ZERO" input must produce negative current in the write head and during the second half it must produce positive current in the write head. It will thus be evident that the recorded data will be characterized by always having a flux change during the second half period regardless of the nature of the input data. Furthermore, the direction of such flux change will always be of one polarity for a binary ONE and the opposite polarity for a binary ZERO. 

1. In a programmed manipulator apparatus, the combination of, a manipulator arm, means for moving said arm in a plurality of different axes, means for developing command signals representing a desired position of said arm in each of said axes, means for developing a position signal representing the position of said arm in each of said axes, comparing means common to said axes for comparing command and position signals and developing an error signal proportional to the difference therebetween, and means for sequentially connecting said comparing means to different command and position signal combinations corresponding to movement in different ones of said axes during different periods in a repetitive multiplex scanning cycle.
 2. The combination of claim 1, wherein there is provided a storage circuit for each of said axes, and means for distributing error signals to said storage circuits during the multiplex period when the corresponding command and position signals are connected to said comparing means.
 3. The combination of claim 2, wherein said distributing means is effective only during the latter portion of each multiplex period of said multiplex scanning cycle.
 4. The combination of claim 2, wherein said comparing means includes means for developing a digital error signal representing the numerical difference between said command and position signals, and means for converting said digital error signal into an analog error signal which is successively applied to said storage circuits.
 5. The combination of claim 4, wherein said analog signal has a velocity-position characteristic which is in the shape of a parabola.
 6. The combination of claim 5, wherein said arm moving means including hydraulic actuator means and servo valve means for controlling said hydraulic actuator means, said servo valve means having a control characteristic which is inversely related to said velocity-position characteristic of said analog signal.
 7. In a programmed manipulator apparatus, the combination of, a manipulator arm, hydraulic actuator means for moving said arm in a given axis, servo valve means for controlling said actuator means, electromagnetic means for controlling said servo valve means, said servo valve means having a square law control characteristic, means for developing a command signal corresponding to the distance to be moved in said axis, means for developing a position signal corresponding to the position of said arm in said axis, means for comparing said position signal with said command signal to derive an error signal having a velocity-position error characteristic opposite to that of said servo valve means, and means for supplying said error signal to said electromagnetic means.
 8. In a programmed manipulator apparatus, the combination of, a manipulator arm, means for moving said arm along a predetermined path, means for developing a digital command signal representing a desired position of said arm, means for developing a digital position signal representing the actual position of said arm, means for comparing said command and position signals to develop a digital error signal, a ladder network, means coupling individual digits of said error signal to different levels of said ladder network, means for combining the outputs of a plurality of levels of said ladder network to provide an analog error signal the shape of which is in the form of a parabola, and means for applying said analog error signal to said arm moving means to move said arm to said desired position.
 9. The combination of claim 8, wherein said arm is moved in a plurality of axes and said comparing means is sequentially connected to different command and position signal combinations corresponding to movement in different ones of said axes during a multiplex cycle, a storage circuit for each of said axes, and means for distributing said analog error signal to said storage circuits during the multiplex period when the corresponding command and position signals are connected to said comparing means.
 10. The combination of claim 1, wherein said position and command signals are digital and said comparing means develops digital error signals equal to the difference therebetween, said comparing means being also arranged to develop a final carry or borrow pulse when one of said position and command signals is larger than the other, and direction determining means controlled in part by said final carry or borrow pulse for controlling the direction of movement of said arm moving means along the corresponding axis.
 11. The combination of claim 10, wherein there is provided means for developing a control signal when said command signal and said position signal are not equal, and means for controlling in part said direction determining means by said control signal.
 12. In a programmed manipulator apparatus, the combination of, a manipulator arm, means for moving said arm in a plurality of axes, a magnetic storage medium, encoder means for developing a plurality of binary code signals representing the absolute position of said arm in said plurality of axes, means for developing successive clock periods in successive program intervals, recording means arranged to develop a flux change of one polarity in said medium during the latter half of any one of said clock periods which represents a binary digit of ''''1'''' and arranged to develop a flux change of opposite polarity in said medium during the latter half of any one of said clock periods which represents a binary digit of ''''0,'''' and teach control means for controlling said recording means in accordance with said encoder signals to record binary code signals on said medium corresponding to a particular position of said manipulator arm.
 13. The combination of claim 12, wherein said storage medium comprises a continuously rotating storage drum, and said recording means includes a plurality of heads adjacent the periphery of said drum, repeat control means for utilizing said heads to produce command signals corresponding to said recorded flux changes, means for comparing said command signals with signals from said encoder means and developing error signals equal to the differences therebetween, and means utilizing said error signals to move said arm to different positions.
 14. In a programmed manipulator, the combination of, a manipulator arm, means for moving said arm along a pluraliTy of axes, encoder means for developing a digital signal corresponding to the absolute position of said arm in one of said axes, means for developing a sequence of digital command signals corresponding to desired positions of said arm along said one axis, means for comparing said encoder signal and one of said command signals in said sequence to develop an analog error signal equal to the difference therebetween, means responsive to said analog error signal for controlling said moving means to move said arm along said one axis in the direction to reduce said analog error signal, means for developing an artificial coincidence signal when said analog error signal is reduced to a predetermined magnitude, and means responsive to said artificial coincidence signal for connecting the next command signal in said sequence to said comparing means.
 15. The combination of claim 14, wherein said artificial coincidence signal is produced while said analog error signal has a value representing a distance equal to a substantial percentage of the total movement of said arm in said one particular axis.
 16. The combination of claim 14, wherein said comparing means develops a digital error signal, means for converting said digital error signal into a corresponding analog error signal, a reference voltage, and means for comparing said analog error signal with said reference voltage to develop said artificial coincidence signal.
 17. The combination of claim 16, wherein said reference voltage is adjustable, thereby to vary the position along said one axis at which said artificial coincidence signal is produced.
 18. In a programmed manipulator, the combination of, a manipulator arm, means for moving said arm along first and second axes, encoder means for developing first and second encoder signals corresponding to the position of said arm in said first and second axes, means for developing command signals corresponding to desired positions of said arm in said first and second axes, means for comparing said first and second encoder signals with their respective command signals to develop first and second error signals equal to the differences therebetween, and means for developing an artificial coincidence signal when both said first and second error signals have values representing a distance equal to a substantial percentage of the total movement of said arm in the respective ones of said first and second axes.
 19. The combination of claim 18, wherein reference means are provided in association with said artificial coincidence signal developing means, and means for comparing said error signals with said reference means.
 20. The combination of claim 19, wherein said reference means is an adjustable voltage source, adjustment of said source being effective to vary the position along each axis at which said artificial coincidence signal is produced.
 21. In a programmed manipulator, the combination of, a manipulator arm movable along a plurality of axes, program means including a series of command signals specifying a sequence of positions to which said arm may be moved, control means responsive to said series of command signals for successively moving said arm toward the positions indicated by two successive ones of said command signals, and means modifying movement of said arm so that said arm moves toward the next position in the sequence before it reaches the positions indicated by said two command signals, the distance between the desired command signal position and the point at which said modifying movement commences being a substantial percentage of the total movement of said arm in at least one of said axes.
 22. The combination of claim 21, wherein means are provided for adjustably varying the point at which said modifying movement commences independently of said program means.
 23. In a programmed manipulator apparatus, the combination of, a manipulator arm mounted on a base member, means for moving said arm along a plurality of axes, storage means, means for storing digItal information in said storage means, encoder means connected to said arm and arranged to develop digital encoder signals corresponding to the absolute position of said arm in each of said axes, a remote teach control assembly interconnected with said storing means through a single flexible cable and adapted to be gripped by a teaching operator, said teach control assembly having a physical shape which simulates generally the physical shape of said manipulator arm, means including push buttons located on said assembly for controlling said moving means to move said arm to a desired position, said push buttons being located on said assembly at points which are physically correlated with desired movement of said arm in each of said axes, a record button located on said assembly, and means including said record button for controlling said storing means to store the digital encoder signal corresponding to said desired position in said storage means.
 24. The combination of claim 23, wherein said manipulator arm is movable along an in-and-out axis and two of said push buttons are located on the forward and rearward ends of said teach control assembly for controlling the in motion and out motion respectively of said arm.
 25. The combination of claim 23, wherein said manipulator arm is movable in a down-up axis, and two of said push buttons are located on the top and bottom surfaces of said teach control assembly for controlling the down motion and up motion respectively of said arm.
 26. The combination of claim 23, wherein said manipulator arm is provided with a pivoted hand on the outer end thereof which is movable in a wrist bend axis, and two of said push buttons are located on the top and bottom surfaces of said teach control assembly for controlling the wrist down motion and wrist up motion respectively of said hand.
 27. The combination of claim 23, wherein said manipulator arm is provided with a pivoted hand on the outer end thereof which is movable in a wrist swivel axis, and two of said push buttons are located on the right and left sides of said teach control assembly for controlling the wrist left swivel motion and wrist right swivel motion respectively of said hand.
 28. The combination of claim 23, wherein said manipulator arm is movable in a rotary movement about a vertical axis, and two of said push buttons are located on the right and left sides of said teach control assembly for controlling the rotary left motion and rotary right motion respectively of said arm.
 29. In a programmed manipulator apparatus, the combination of, a manipulator arm, a rotatably mounted vertically extending member, means for supporting said arm on the upper end of said member, a ring gear connected to said member, a rack in engagement with said ring gear, hydraulic cylinder means for moving said rack so that said arm is rotated about the vertical axis of said member, a piston the end of which is in sliding engagement with said rack, and means for exerting a force on said piston which is greater than the maximum separating forces produced between said ring gear and said rack when said arm is accelerated and decelerated. 